Cannabis is a genus of flowering plants in the Cannabaceae family whose dried flower preparations (Cannabis sativa, Cannabis indica, and their hybrids) have been used by humans for fiber, medicine, and intoxication for at least 5,000 years. The primary psychoactive constituent of cannabis is tetrahydrocannabinol (THC), a partial agonist at cannabinoid CB1 receptors distributed throughout the brain. At typical recreational doses, cannabis produces a distinctive complex of effects including euphoria, relaxation, altered sensory perception, increased appetite, reduced anxiety, and at higher doses, psychedelic-adjacent cognitive changes. No other broadly used psychoactive substance has a pharmacological mechanism as novel as the endocannabinoid system — cannabis essentially hijacks a system of neuromodulatory lipid-based signaling that evolved to regulate fundamental processes including pain, memory, appetite, and emotional processing.
The cannabis experience is highly context and dose dependent, modulated by the ratio of THC to cannabidiol (CBD), the terpene profile of the preparation, the route of administration, and crucially, the user's experience level, set, and setting. Novice users and those with THC sensitivity can experience significant anxiety and paranoia even at doses that experienced users tolerate comfortably — this is one of the most consistent findings in cannabis pharmacology and accounts for the large variation in individual responses. Community experience on Reddit reflects this: experienced users frequently describe cannabis as capable of being used "as a very potent psychedelic" through tolerance breaks and high-dose edibles, while others describe it as producing primarily derealization and anxiety.
Cannabis is simultaneously one of the most socially complex substances in contemporary society: it is the most widely used illicit substance globally, legally available for medical and/or recreational use across much of North America and a growing number of countries, deeply integrated into some cultures as a spiritual and therapeutic tool, and also responsible for a diagnosable use disorder in approximately 9% of users (17% of those who begin in adolescence). The discourse about cannabis in online communities reflects this complexity — its potential as a harm reduction tool for reducing alcohol consumption exists alongside documentation of cannabis use disorder, with both perspectives represented honestly.
Medically, cannabis and its derived compounds (including synthetic cannabinoids and CBD) have evidence-supported applications including nausea and vomiting reduction (particularly in chemotherapy), appetite stimulation in wasting conditions, neuropathic pain, spasticity in multiple sclerosis, and certain seizure disorders (epidiolex, a purified CBD formulation, has FDA approval for specific epileptic syndromes). The medical evidence base continues to expand with ongoing legalization.
